Radiometer and oxygen lance combination



Dec. 3, 1968 F. ENGEL ET AL RADIOMETER AND OXYGEN LANCE COMBINATIONFiled Feb. 12, 1965 2 Sheets-Sheet 2 I N VEN TORS. FEEDER/K E/VGELALWY/V F W/EB BY Mfi ATTORNEY United States Patent 3,413,852 RADIOMETERAND OXYGEN LANCE COMBINATION Frederik Engel, Greenwich, and Alwyn F.Wiehe, Ridgefield, Conn., assignors to Barnes Engineering Company,Stamford, Conn., a corporation of Delaware Filed Feb. 12, 1965, Ser. No.432,095 4 Claims. (Cl. 73355) This invention relates to an oxygen lanceand radiometer combination for measuring temperatures in steel furnacesand other apparatus where a cooled lance is used for introducing gases.

The problem of measurement of the temperature of molten steel infurnaces such as open hearth converters and the like has long been aserious one. In the older Bessemer converters temperature was frequentlydetermined by the appearance of the flame from the converter. This wasnot very accurate and resulted in a considerable variation in quality ofthe steel produced. The problem became much more acute with the modernoxygen process in which oxygen is introduced from above the melt througha 50 feet long water cooled lance. This process has constituted so greatan improvement that steel furnaces are rapidly being converted to usethe prOcess. However, for best operation an accurate knowledge of thetemperature is necessary and this has created a serious problem because,of course, if the temperature is not maintained right and a steel meltis spoiled the costs of such an occurrence can be very high. Also,though perhaps less spectacularly serious, if the temperature is notmaintained accurately the quality of the steel produced may not be anoptimum.

Various proposals have been made to measure the temperature of thesteel, for example, expendable thermocouple probes have been used butthis has not proven to be entirely satisfactory as the probe has to beactually lowered or dropped into the melt.

At first glance it would seem that the problem might be solved byradiometry using a radiation pyrometer looking down on the surface ofthe steel melt. This, however, is not very practical because the surfacemay become covered with a thin layer of slag or other impurities and sowrong temperature readings or at least inaccurate temperature readingsresult.

The first oxygen lances used were open at the bottom, the wall of thelance being water cooled and it might appear practical to place aradiometer at the top of the lance. However, this early form of lance isno longer preferred and modern lances have their bottoms closed exceptfor a number of holes, the longitudinal axis of which is on a slant withrespect to the lance body proper. Typically there may be three holespointing out at an angle that may be of the order of Such a lance cannotbe used with a radiometer because the radiometer would see the bottomwall, the temperature of which bears but little relation to the actualtemperature of the steel.

The present invention solves the problem of radiometric measurement in amodern oxygen lance and is free from the disadvantages of othertemperature measurements which have been proposed. Essentially in thepresent invention one or more, usually three, radiometers are located inthe water chamber nearest the inner wall of the lance. The structure ofthe lance is altered by providing side tubes extending through the innerwall into the water space and having the radiometers mounted at theirupper end. The directions of the tubes are such that they aresubstantially aligned with the slanted tubes at the bottom of the lance.Radiation from the surface of the steel or, as will be pointed out inmore detail below, other materials located near the surface such as hotgases,

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pass up the inclined side tubes in the inner wall of the lance andstrike the entrance pupils of the radiometers. Normally a protectivewindow is provided and one or more bandpass filters. It is also possibleto utilize beam directing means such as a prism in the entrance pupil ofthe radiometer but for practical purposes this is ordinarily notnecessary as the amount of radiation available is high and theinclination of the tubes in the bottom of the lance is small. Therefore,in preferred practical instruments a beam directing means is eliminatedbecause the energy loss is small and the remaining energy is still morethan sufficient for good radiometer response. However, the presentinvention does not exclude a more sophisticated structure with beamdirecting means.

The location of the radiometers in the coolant passage of the lancebrings them fairly close to the angled tubes at the end of the lance,for example, about three feet. This permits viewing of a larger area ofthe surface of the steel and so avoids possible spurious results ifthere are small areas, the temperature of which differs markedly fromthat of the melt as a whole. When a radiometer was used at the top of anold style lance the path to the steel was so long, up to nearly 50 feet,that collecting optics were needed and only a relatively small surfaceof steel could be viewed. This introduced a further disadvantage in thatlocal hot spots might give an incorrect reading. The location of theradiometer, preferably in the inner coolant passage of the lance,permits a normally quite stable environment at relatively moderatetemperature far below the boiling point of water. This minimizes anyeffects of instrument temperature on readings. However, if desired theradiometer may be provided with a temperature sensing element such as athermocouple or thermistor so that excessive temperatures can be avoidedwhen the lance is being built and the outer wall welded The radiometersare provided with electronics which produce an output signal that can beused for temperature readout, preferably at a location removed from theactual furnace. The present invention is not concerned with any new formof electronics or any new type of readout instruments. The exact designof these elements, therefore, does not form any part of the presentinvention and so will not be shown in detail. Although they are not newin the present invention suitable electronics and readout elements arenecessary to utilize the invention practically.

The radiometers present no very serious problem. The dimensions of thewater channel, however, dictate a long and narrow radiometer with itsassociated electronics and in this shape of radiometer it is normallynot necessary to use collecting optics. However, as pointed out above,the present invention is not broadly limited to any particularradiometer for, of course, the exact shape and dimensions of theradiometers are a mere matter of proper engineering design.

Although any suitable radiometer can be used, there i an importantadvantage in utilizing radiometers as described in the Weiss Patent3,161,775, Dec. 15, 1964 and such radiometers are preferred and in amore specific aspect of the invention constitute part of the combinationclaimed. The Weiss radiometers use photomultiplier tubes for detectionand utilize wavelengths of radiations which are much shorter, forexample, from /2 to /6 the wavelength of that for maximum radiation.This permits an important additional advantage. When operating aconsiderable distance from the wavelength for maximum radiation thechanges in radiation with temperature follow a much higher power ofabsolute temperature, than is the case at the wavelength for maximumradiation. For example, at maximum radiation wavelength the response isin proportion to the fifth power of the absolute temperature but atone-half the wavelength the response is in accordance with a much higherpower of the absolute temperature. Since the emissivity of the body, thetemperature of which is to be measured, is a linear function it becomesso small in comparison to the effect of a change in temperature that itcan be practically neglected. Even with an enormous emissivity variationof 2 to l the accuracy is better than percent and so the temperaturemeasurements may be considered practically independent of emissivity ofthe surface of the steel. This is a very great practical advantagebecause surface scum can change the emissivity quite markedly eventhough it is, to considerable extent, blown away by the oxygen blast.Therefore, in a preferred aspect of the present invention for the mostperfect practical instruments, the greater precision of the Weissradiometers is of real importance and so this type of radiometer ispreferred and constitutes a part of the combination of the preferredspecific embodiment of the present invention.

Apart from the desirability of using a Weiss radiometer with its narrowbandpass filter the present invention is not particularly concerned withthe elements which are used in the radiometer and its electronics,except for the practical requirements of operating at an elevatedtemperature which may reach 100 C. in the case of a defectivecirculation of water in the lance. The radiometer must also have a highdegree of shock resistance bebecause when not in use lances are subjectto fairly rough treatment in a steel mill.

In the case of electronic elements temperature is practically the onlyproblem except for the detector. Photomultiplier tubes, as described inthe Weiss patent, are preferred and when this type of radiometer is usedphotomultiplier tubes must be chosen which operate reliably even underconditions of severe shock, vibration and fairly elevated temperature.There are available today commercially photomultiplier tubes which arecompletely incapsulated except for a small radiation window and whichhave self-contained voltage divider resistors for the various dynodes sothat only three wires are needed for ground, high voltage and signaloutput. This type of photomultiplier tube is preferred. It is, however,an advantage of the present invention that a common commerciallyavailable photomultiplier tube can be used and specially fabricateddetectors are, therefore, not necessary.

The Weiss radiometers utilize wavelengths from onehalf to one-sixth thatfor maximum black body radiation. In the case of the steel furnace thetemperatures may vary from 1200 to about 1800 C. This corresponds to Aof from about 1.95 1. to 1.45 For maximum precision one would ordinarilyutilize wavelengths in the near ultraviolet. In fact the Weissradiometers are often loosely referred to as ultraviolet radiometers. Inthe case of the present invention, however, another result can beobtained under special circumstances by departing somewhat from thetheoretical maximum precision as set out in the Weiss patent thoughstill well within its operating range. Thus it has been found that forthe radiometer or radiometers which are receiving radiation from thesurface of the molten steel, a narrow band of radiation in the yellowgreen at about 560 me, can be used to give good precision even withquite large variations in emissivity and it performs the additionalfunction of being blind to strong emission lines of carbon monoxide andcarbon dioxide which are the most common gases which might beencountered having strong emission lines.

The present invention has a further advantage when more than oneradiometer is used, for example, when three are used, in the case of themost usual configuration of modern oxygen lances. The use of multipleradiometers permits an added protection against radiometer failure and acheck of one radiometer reading against another. Radiometers are quiterugged instruments and have long useful lives but no instrument is freefrom the possibility of breakage or malfunction and so if more than oneradiometer is present the added redundancy enormously decreases thepossibility of complete failure with the large losses which can resultfrom a spoiled steel melt. The additional cost of more than oneradiometer is quite small when amortized over their long lives.Therefore. there is a real practical advantage in using more than oneradiometer per lance even though it is not desired to measure radiationfrom gaseous emission bands.

The Weiss radiometer in its preferred form presents an importantadditional advantage. When photomultiplier tubes are used it is possibleto make measurements at .1 fixed current, for example, 10 ,ua., byvarying the high voltage on the anode of the photomultiplier tube. Thiseffects a logarithmic compression which is extremely valuable as thetemperature range in a particular steel melt may run over severalhundreds of degrees from start to finish and this can result in aradiation variation of as much as 400:1. The invention is not, ofcourse, limited to the use of a photomultiplier tubes as a radiationdetector and the compression feature described above. If a differenttype of detector is used the electronics are preferably of logarithmicor semilogarithmic type to effect the necessary compression. When thepreferred form of Weiss radiometer is used the compression is effectedby the operation of the photomultiplier tube itself at constant currentand this is the preferred modification.

The smaller angled tubes at the bottom of the lance in conjunction withthe short path radiometers also permit an additional advantage, namelythat it is easier to calibrate the instrument when the lance is out ofthe steel melt because the area of such a calibrating source of knowntemperature is considerably smaller and so makes calibration easier. Itis an advantage of the present invention that the important improvedresults are obtained without any compromise and even with additionaladvantages.

The operation of a Weiss radiometer in order to increase precision bymeasuring at a much shorter wavelength than that corresponding tomaximum radiation requires only that the wavelength band be at leastsufiiciently short. In other words, a long wave cutoff filter isessential. If it is desired to avoid interference from emission bands ofgases, of course, the range of radiation must be much narrower and sothat filters used have to have a short wave cutoff as well as a longwave cutoff. In many cases the gas emission interference is not seriousand then the filters can be simpler and cheaper providing only for along wave cutoff.

The invention will be described in greater detail in conjunction with atypical oxygen lance, only one radiometer. however, being shown. Theinvention will also be described in conjunction with the drawings inwhich:

FIG. 1 is a vertical section through one side of an oxygen lance, and

FIG. 2 is a horizontal section above the radiometer looking down at theend of the lance.

The lance itself is made up with an outer wall 1, a middle Wall 2 and aninner wall 4. This forms two channels 3 and 5 through which watercirculates, down in the inner channel and up in the outer channel. Aninclined tube 6 is mounted in the inner wall 4 having an inclinationcorresponding to that of a tube 18 which is shown in FIG. 2. At the topof the tube there is a mounting flange 7 on which is mounted a window 8,a sharp cutting filter 9 and the radiometer with a photomultiplier tube10 forming its entrance pupil and incapsulated as shown at 11 and itselectronics at 12. Since the design of the radiometer is not ditferentfrom that described in the Weiss patent except for its elongated shape,it is not shown in detail but only diagrammatically. From theelectronics three wires 15 emerge passing through a connector 14 mountedon an upper flange 16. Suitable water tight seals are shown, forexample, at 19 to prevent any possibility of water getting into theradiometer and to provide a suitable firm seating therefor.

If more than one radiometer is used, for example three, there will bethree side tubes through the inner wall of the lance each oneregistering down a particular tube 18. It should be noted that theopenings in the bottom wall 20 of the lance are circular but the viewthrough the inclined tube is more or less lenticular as shown at 18.

The invention has been described in conjunction with structure in Whichthe inclined tubes extend only into the inner coolant passageway and theradiometers are located therein. It is, of course, possible for theinclined tubes to extend further either into the outer coolantpassageway to mount the radiometers in the outer coolant passageway.While such modifications are operative and are not excluded from theboard aspects of the present invention the preferred modificationillustrated in the drawings has marked advantages. It is cheaper, andthe temperature environment in the inner coolant passage is better forradiometer operation. Therefore, this modification is preierred.

I claim:

ll. An oxygen lance and radiometer structure comprising:

(a) a lance with cylindrical walls forming two coolant passages,

(b) a bottom wall with at least one opening angled out at a small angle,

(c) at least one inclined tube in the inner wall of the lance extendingupwardly at least onto the inner coolant passage and having its axisaligned with the axis of one of the openings in the bottom of the lance,

(d) a radiometer mounted on the upper end of said inclined tube havingmeans for selecting a predetermined wavelcngth band of radiation andbeing 10- cated so that the entrance pupil of the radiometer receivesradiation through the inclined tube, and (e) the radiometer beingprovided with a radiation detector responsive to the predeterminedradiation range and electronics receiving signal from said detector andproducing an output which is a function of temperature of the materialswhose radiations are received by the radiometer. 2. A lance andradiometer structure according to claim 1 in which the inclined tubeextends only into the inner coolant passage and the radiometer body islocated in said passage.

3. A lance and radiometer structure according to claim 1 in which theradiometers are provided with filtering means including at least a longwave cutotf to restrict the radiation to a wavelength not longer thanone-half the wavelength of maximum radiation of the steel for the rangeof temperatures being measured, whereby emissivity changes in thesurface do not significantly interfere with accuracy of reading.

4. A lance and radiometer structure according to claim 3 in which aplurality of radiometers are used each one aligned to receive radiationfrom a different inclined tube.

References Cited UNITED STATES PATENTS 1/1950 Mead 73-355 XR 12/1964Weiss 73-355 XR

1. AN OXYGEN LANCE AND RADIOMETER STRUCTURE COMPRISING: (A) A LANCE WITHCYLINDRICAL WALLS FORMING TWO COOLANT PASSAGES, (B) A BOTTOM WALL WITHAT LEAST ONE OPENING ANGLED OUT AT A SMALL ANGLE, (C) AT LEAST ONEINCLINED TUBE IN THE INNER WALL OF THE LANCE EXTENDING UPWARDLY AT LEASTONTO THE INNER COOLANT PASSAGE AND HAVING ITS AXIS ALIGNED WITH THE AXISOF ONE OF THE OPENINGS IN THE BOTTOM OF THE LANCE, (D) A RADIOMETERMOUNTED ON THE UPPER END OF SAID INCLINED TUBE HAVING MEANS FORSELECTING A PREDETERMINED WAVELENGTH BAND OF RADIATION AND BEING LOCATEDSO THAT THE ENTRANCE PUPIL OF THE RADIOMETER RECEIVES RADIATION THROUGHTHE INCLINED TUBE, AND (E) THE RADIOMETER BEING PROVIDED WITH ARADIATION DETECTOR RESPONSIVE TO THE PREDETERMINED RADIATION RANGE ANDELECTRONICS RECEIVING SIGNAL FROM SAID DETECTOR AND PRODUCING AN OUTPUTWHICH IS A FUNCTION OF TEMPERATURE OF THE MATERIALS WHOSE RADIATIONS ARERECEIVED BY THE RADIOMETER.